The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingAntenna coil open / short
Description
The transponder key coil receives key code signals from the transponder chip
in the key grip. The coil
built into the transponder key amplifier amplifies the key code signals and
outputs the signal to the
transponder key ecu.
Wiring diagram
Inspection procedure
R ...
Rear differential carrier assembly
Components
...
Engine compartment
Engine coolant reservoir
Engine oil filler cap
Battery
Brake fluid reservoir
Fuse box
Radiator
Condenser
Electric cooling fans
Engine oil level dipstick
Washer fluid tank
Engine oil
With the engine at operating temperature and turned off, check the oil
level on the dips ...